Heat Transfer

Heat can transfer through conduction, convection, or radiation (Tillery, 2008).  Conduction is the transfer of heat by or through the means of a conductor. Convection is the circulatory motion that occurs in a fluid at a no uniform temperature. Radiation is emitting radiant energy in the form of waves or particle means by rays.

Prior to beginning the experiment, I gathered all materials (four mugs, a measuring cup, thermometer, a clock, a cotton sock, a plastic zip loc bag, aluminum foil, and a coffee filter). Next, I made a hypothesis that the cotton sock would make the best insulator. In an effort to achieve maximum results on equal starting water temperature, my husband assisted me with filling the mugs to the marked line. The starting temperature was 117˚ degrees Fahrenheit and we both covered two mugs and started the clock. After thirty minutes had passed, I removed all four substances and recorded my results in the chart below:

Substance	Temperature
Aluminum Foil	99˚F
Coffee Filter	102˚F
Cotton Sock	100˚F
Zip-Loc Bag	105˚F

* The starting temperature was 117˚ degrees.

The zip-loc bag makes the best insulator if these four substances are considered.

If I was to repeat the experiment, I would have chosen items such as paper, a silk scarf, and a wool sock. I would allow my students to conduct this experiment using warm or cold water, to reduce potential hot water hazards.

Pendulum Swings

Prior to beginning this experiment, I hypothesized that the lighter pendulum would come to rest more quickly. My hypothesis was based on my prior knowledge of gravity, mass, and inertia. In beginning the experiment, I tied the string to the pencil before taping the pencil to the countertop as this was a constant since I did not untie the string from the pencil for the duration of the experiment. Taping the pencil to the countertop allowed free oscillation of the pendulum. Next, I attached the other end of the string to the smaller washer, which had a quarter inch diameter in length. I dropped the pendulum from the lowest point of the pencil that was hanging off of the countertop and allowed the pendulum to swing for twenty five seconds. The same procedure was repeated for the next pendulum, which was made using a washer with a half inch diameter. Although the mass of the washers were different, both pendulums completed thirteen rounds. The release points of the pendulums, the length of the string, and the amount of time allotted for the swings were constants. My hypothesis was correct since the lighter pendulum came to rest first.

My students would probably hypothesize that the heavier pendulum would come to rest quicker after completing the “Falling Bodies Experiment” last week and noticed that the heavier objects reached the floor first. Challenges came when I tried to accurately perform the experiment using the same release height and force for both pendulums. Students would be provided the opportunity to measure their strings, discuss why their data differs from their classmates, and debate about the effects of the washer sizes. Students will also have the opportunity to drop their pendulums from whatever reasonable height they choose. “When students gain experience with problem solving, they have the potential to invent new ways of doing things”. Students may be challenged with releasing their pendulums at the same height or accurately starting and stopping the stopwatch.